linux-kernel - [PATCH v2 09/16] iio: adc: ad7768-1: remove unnecessary locking

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Message-ID: <df331cd681feb756d06df4173f67f75ec655bfb2.1737985435.git.Jonathan.Santos@analog.com>
Date: Mon, 27 Jan 2025 12:13:08 -0300
From: Jonathan Santos <Jonathan.Santos@...log.com>
To: <linux-iio@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
CC: Jonathan Santos <Jonathan.Santos@...log.com>, <lars@...afoo.de>,
        <Michael.Hennerich@...log.com>, <marcelo.schmitt@...log.com>,
        <jic23@...nel.org>, <robh@...nel.org>, <krzk+dt@...nel.org>,
        <conor+dt@...nel.org>, <jonath4nns@...il.com>,
        <marcelo.schmitt1@...il.com>
Subject: [PATCH v2 09/16] iio: adc: ad7768-1: remove unnecessary locking

The current locking is only preventing a triggered buffer Transfer and a
debugfs register access from happening at the same time. If a register
access happens during a buffered read, the action is doomed to fail anyway,
since we need to write a magic value to exit continuous read mode.

Remove locking from the trigger handler and use
iio_device_claim_direct_mode() instead in the register access function.

Signed-off-by: Jonathan Santos <Jonathan.Santos@...log.com>
---
v2 Changes:
* New patch in v2. It replaces the guard(mutex) patch. 
---
 drivers/iio/adc/ad7768-1.c | 23 ++++++++++-------------
 1 file changed, 10 insertions(+), 13 deletions(-)

diff --git a/drivers/iio/adc/ad7768-1.c b/drivers/iio/adc/ad7768-1.c
index 17a49bf74637..5e2093be9b92 100644
--- a/drivers/iio/adc/ad7768-1.c
+++ b/drivers/iio/adc/ad7768-1.c
@@ -271,16 +271,16 @@ static int ad7768_reg_access(struct iio_dev *indio_dev,
 	struct ad7768_state *st = iio_priv(indio_dev);
 	int ret;
 
-	mutex_lock(&st->lock);
-	if (readval) {
+	ret = iio_device_claim_direct_mode(indio_dev);
+	if (ret)
+		return ret;
+
+	if (readval)
 		ret = regmap_read(st->regmap, reg, readval);
-		if (ret)
-			goto err_unlock;
-	} else {
+	else
 		ret = regmap_write(st->regmap, reg, writeval);
-	}
-err_unlock:
-	mutex_unlock(&st->lock);
+
+	iio_device_release_direct_mode(indio_dev);
 
 	return ret;
 }
@@ -495,18 +495,15 @@ static irqreturn_t ad7768_trigger_handler(int irq, void *p)
 	struct ad7768_state *st = iio_priv(indio_dev);
 	int ret;
 
-	mutex_lock(&st->lock);
-
 	ret = spi_read(st->spi, &st->data.scan.chan, 3);
 	if (ret < 0)
-		goto err_unlock;
+		goto out;
 
 	iio_push_to_buffers_with_timestamp(indio_dev, &st->data.scan,
 					   iio_get_time_ns(indio_dev));
 
-err_unlock:
+out:
 	iio_trigger_notify_done(indio_dev->trig);
-	mutex_unlock(&st->lock);
 
 	return IRQ_HANDLED;
 }
-- 
2.34.1